Radio/microwave frequency receivers and transmitting systems typically rely on a superheterodyne architecture to couple high-frequency signals from the antenna to a base-band processor. Superheterodyne frequency receivers and transmitting systems spanning many octaves of frequency coverage typically require multiple conversion steps and intermediate frequencies to down-convert to a final processing frequency. Frequency filters are heavily relied upon to channelize bands of operation and reject interference. Unfortunately, these filters typically comprise a large volume of the overall system size and are not amenable to monolithic fabrication, requiring extensive and costly touch labor (also direct labor, factory labor costs that can be easily traced to individual units of product). Radio/microwave frequency receivers and transmitting systems also rely on highly linear and low-loss switches to select between channels.
Conventional approaches to reducing transceiver complexity include direct-conversion transceivers, SAW filters, high-Dk distributed element filters, varactor-based agile filters, and FET semiconductor switches. However, direct-conversion transceivers suffer from DC offset errors and poor second order intermodulation performance. SAW filters are inherently narrow band, lossy, have poor group delay response, and are not amenable to monolithic integration. High-Dk distributed element filters are lossy and still consume appreciable size at lower frequencies. Varactor-based agile filters typically have high loss, modest intermodulation performance, limited tuning range, and complex biasing requirements. FET semiconductor switches are lossy, exhibit poor isolation, and are prone to intermodulation distortion.
Consequently, it would be desirable to reduce the size and complexity of transceivers with highly linear, low-loss filters which can be monolithically integrated.